<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<script type="text/javascript">
	var xxxx="HELLO WORLD!";
	xxxx=xxxx.replace("WORLD","JACK");
	document.write("</br>"+xxxx);//替换
</script>	
</body>
</html>